Cyclopropyl methylketone is used to manufacture a variety of agricultural chemicals and pharmaceuticals. One route to prepare this compound begins with .alpha.-acetyl-.gamma.-butyrolactone. In this process, 5-chloro-2-pentanone is first formed by reacting the .alpha.-acetyl-.gamma.-butyrolactone with an acid. This intermediate is then isolated by ether extraction and reacted with 50-wt % aqueous sodium hydroxide. This second reaction forms cyclopropyl methylketone, which is then purified by distillation. See Cannon, G. W.; Ellis, R. C.; and Leal, J. R., Org. Synth. Coll., Vol. IV, p. 597.
Another route to prepare cyclopropyl methylketone also begins with .alpha.-acetyl-.gamma.-butyrolactone. In this process, the cyclopropyl methylketone is formed directly by heating .alpha.-acetyl-.gamma.-butyrolactone in the presence of a halide salt, and preferably an organic solvent. See U.S. Pat. No. 5,254,739 to Hunston and others.
The problem with these and other methods is that they are impractical on a large scale. High concentrations of base are expensive and require special handling techniques. Organic solvents are difficult, if not impossible, to discard under current EPA regulations, and typically must be recovered with distilling operations. As a result, what is needed is a more economical process to prepare cyclopropyl methylketone, and this invention addresses that need.